Method for improving strength and radial uniformity of high-temperature alloy inertia friction welding joint

Abstract

The invention provides a method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint, and belongs to the technical field of solid-phase welding. The inertia friction welding technology is adopted for conducting high-quality connection on the high-temperature alloy rotating workpieces, due to the fact that heat generated by a connector interface and pressure distribution are not uniform, recrystallization grain growth is affected, radial tissue and performance distribution of a connector is not uniform, then the connector is induced to form a performance weak area, connector deformation and disharmony are caused, and the high-temperature alloy rotating workpieces are subjected to high-quality connection. The joint strength is obviously influenced. Through the synergistic effect of solid solution strengthening and two-stage aging strengthening, the strength of the joint is improved, the radial structure and performance uniformity of the joint are remarkably improved, the dynamic recovery and dynamic recrystallization process of the joint is promoted, the structure morphology and distribution of a joint strengthening phase gamma'are improved, precipitated phases such as carbides are reduced, and the joint strength is improved. Precise regulation and control of joint tissue and performance are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of solid phase welding, and in particular relates to a method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint. Background Art

[0002] With the urgent need for the development of high thrust-to-weight ratio of aero-engines, high-temperature alloys have excellent creep resistance, high temperature resistance and corrosion resistance, and have become the preferred material for hot-end components such as rotors of high-performance aero-engines. Inertia friction welding, as a typical solid-phase welding technology, can effectively avoid defects such as pores, cracks and slag inclusions that are prone to occur in traditional fusion welding. However, the complex and changeable service environment places extremely stringent requirements on joint strength. In addition, due to the uneven distribution of heat and pressure at the welding interface, the joint structure and performance show radial non-uniformity, which in turn affects the joint forming quality. Therefore, improving the strength and radial uniformity of high-temperature alloy inertia friction welding joints is of great significance to improving the performance and reliability of hot-end components of aero-engines.

[0003] The literature "Effect of heat treatment process on the microstructure and microhardness of inertia friction welding of FGH96 alloy, Zhang Chunbo, Liang Wu, Zhou Jun, et al., Journal of Welding, 2023, 44(8): 57-62" reported the effect of aging heat treatment on the microstructure and microhardness of inertia friction welding joints of FGH96 alloy. The study found that the content and morphology of the secondary γ′ phase in the weld area after aging treatment were similar to those in the weld state, and the secondary γ′ phase in the center of the weld was completely dissolved; from the center of the weld along the axis, the content of the secondary γ′ phase gradually increased and then tended to be stable; due to the small amount of precipitation of the tertiary γ′ phase, the overall microhardness of the weld area and the thermally affected zone was significantly improved. The secondary γ′ phase can improve the comprehensive performance of the joint through precipitation strengthening and dislocation interaction, but in the prior art, after post-weld aging treatment, the content and distribution of the secondary γ′ phase did not change significantly, especially no obvious strengthening phase precipitation in the weld core area, so the strengthening effect on the joint performance needs to be enhanced.

[0004] The literature "Effect of Aging Treatment on Room Temperature Tensile Behavior of Powder Superalloy Inertia Friction Welded Joints, Zhou Xiaoming, Feng Yefei, Zeng Weihu, et al., Powder Metallurgy Technology, 2021, 39(1): 41-48" reported that the room temperature tensile strength of the weld zone and heat-affected zone after post-weld aging treatment was significantly improved compared with the welded specimen, but the fracture position of the tensile specimen after aging treatment was still located in the weld zone and showed brittle fracture characteristics. The above technology improves the joint strength through post-weld aging treatment, but the tensile fracture position of the joint is still located in the weld, affecting the service behavior of the joint. This is mainly because the post-weld aging treatment has no significant effect on the overall grain change of the joint. The radial inhomogeneity of the joint will induce the formation of a weak performance zone in the joint, resulting in inconsistent joint deformation, which can easily cause joint fracture failure, limiting its application in key components in the equipment manufacturing field.

[0005] It can be seen that in order to solve the bottleneck problems in the above-mentioned prior art, it is urgent to develop a simple and efficient process method to simultaneously promote the improvement of joint strength and radial uniformity, and to achieve precise control of the microstructure and performance of high-temperature alloy inertia friction welding joints. Summary of the invention

[0006] In response to the common problems of poor joint strength and uneven radial structure and performance distribution in the above-mentioned prior art, the present invention provides a method for improving the strength and radial uniformity of high-temperature alloy inertia friction welding joints, and achieves significant improvement in the strength and radial uniformity of welded joints through the synergistic effect of post-weld solid solution + two-stage aging treatment.

[0007] The present invention adopts the following technical solutions:

[0008] A method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint comprises the following steps:

[0009] Step 1: Grind the surface of the high-temperature alloy rotating workpiece to be welded step by step, immerse the polished workpiece in anhydrous ethanol solution for ultrasonic cleaning, and then dry it for standby use;

[0010] Step 2: Clamp the workpieces to be welded at the rotating end and sliding end of the machine tool respectively, and calibrate and adjust the concentricity of the workpieces; weld the workpieces to be welded, and the welding interface achieves metallurgical bonding through processes such as plastic deformation, recrystallization, and diffusion;

[0011] Step 3: Remove the flash inside and outside the inertia friction welding joint of the high-temperature alloy rotating workpiece to meet the process design standards;

[0012] Step 4: Perform solid solution strengthening treatment on the welded joint: heat to the solid solution temperature at a constant heating rate, then keep warm, and then cool naturally to room temperature;

[0013] Step 5: Perform double-stage aging strengthening treatment on the joint after solid solution strengthening: heat to the first aging temperature at a constant heating rate, cool to the second aging temperature at a constant cooling rate after insulation, and naturally cool to room temperature after insulation.

[0014] As a supplement to the technical solution of the present invention, in step 4, the process parameters of the solid solution strengthening treatment are: the solid solution temperature is 1020-1140°C, the preferred value is 1080°C, the solid solution holding time is 1-6h, and the heating rate is 300-600°C / h.

[0015] As a supplement to the technical solution of the present invention, in step 5, the process parameters of the two-stage aging strengthening treatment are: the first-stage aging temperature is 700-800°C, preferably 760°C, and the first-stage aging insulation time is 4-10h; the second-stage aging temperature is 600-700°C, preferably 650°C, and the second-stage aging insulation time is 1-6h; the heating rate is 300-600°C / h, and the cooling rate is 10-200°C / h.

[0016] As a supplement to the technical solution of the present invention, the high-temperature alloy is a nickel-based high-temperature alloy; the nickel-based high-temperature alloy includes FGH98, FGH101, GH4065 or GH4169, etc.

[0017] As a supplement to the technical solution of the present invention, in step 2, the inertia friction welding process parameters are: initial speed of 300-1000r / min, welding pressure of 20-500MPa, moment of inertia of 30-500kg·m 2 .

[0018] As a supplement to the technical solution of the present invention, in step 3, the surface roughness Ra after processing is less than 1.6 μm.

[0019] As a supplement to the technical solution of the present invention, in step 1, the high-temperature alloy rotating workpiece is a tubular structure with an inner diameter of 20 to 100 mm and an outer diameter of 30 to 180 mm.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1) Inertia friction welding technology is used to achieve high-quality connection of high-temperature alloy rotating workpieces, breaking through the defects such as pores, cracks and inclusions that are easily formed during traditional fusion welding, improving the interface bonding state, and providing a new solution for the precision connection of high-temperature alloy components.

[0022] 2) The solid solution strengthening treatment effectively promotes the uniform distribution of alloy strengthening elements such as Cr and Mo, eliminates element segregation, and achieves fine control of the grain size of the joint, thereby improving the radial inhomogeneity of the joint. In addition, after the solid solution treatment, the primary γ' phase is almost completely dissolved, and in the subsequent cooling process, the secondary γ' phase is uniformly precipitated and distributed in the γ matrix, significantly improving the joint strength.

[0023] 3) Through graded aging strengthening treatment, the dispersion precipitation of the tertiary γ' phase is promoted during the cooling process. The pinning effect of the precipitated phase effectively suppresses the abnormal growth trend of the grains in a high temperature environment. Compared with single-stage aging, graded aging can increase the precipitation density of the tertiary γ' phase and regulate the morphology of the precipitated phase, further improving the joint strength and radial uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the solution aging treatment process curve adopted in the embodiment of the present invention;

[0025] Figure 2 The grain distribution of the joint in the welded state of the embodiment of the present invention;

[0026] Figure 3 The grain distribution of the joint in the heat-treated state of the embodiment of the present invention;

[0027] Figure 4 The distribution and morphology of the strengthening phase in different areas of the joint of the embodiment of the present invention are as follows: (a) as welded; (b) as heat treated;

[0028] Figure 5 is the tensile strength of the joint in the welding state and the heat-treated state of the embodiment of the present invention;

[0029] Figure 6 The tensile fracture positions of the embodiments of the present invention in the welded state and the heat-treated state: (a) welded state; (b) heat-treated state. DETAILED DESCRIPTION

[0030] To facilitate the understanding of the technical solution, the present invention provides the following embodiments, specifically selecting FGH96 high-temperature alloy for welding, but is not limited to the above-mentioned high-temperature alloys. The method disclosed in the present invention is also applicable to the regulation of the strength and radial uniformity of inertia friction welding joints of other high-temperature alloys.

[0031] Embodiment 1:

[0032] Step 1: Before welding, use sandpaper of different grits to grind the surface of the high-temperature alloy rotating workpiece with an inner diameter of 28mm and an outer diameter of 62mm step by step. Immerse the grinded workpiece in anhydrous ethanol solution for ultrasonic cleaning for 15 minutes, then use a hair dryer to dry the surface and dry it for later use.

[0033] Step 2: Clamp the workpiece to be welded on the rotating end and sliding end of the machine tool respectively, ensure that the axes of the two coincide, and calibrate and adjust the concentricity of the workpiece. Set the inertia friction welding process parameters: initial speed is 645r / min, welding pressure is 320MPa, and moment of inertia is 388kg·m 2 After the flywheel drives the rotating end workpiece to reach the initial speed, the spindle drive motor separates from the rotating end and begins to enter the free parking state. At the same time, the sliding end workpiece is driven by the hydraulic servo to move toward the rotating end. Under the action of axial pressure, the surfaces to be welded rub against each other to generate heat until they reach a high-temperature plastic state. The high-temperature plastic metal at the welding interface is squeezed out of the interface to form flash. Under the continuous action of friction torque, the speed of the rotating end workpiece gradually decreases until it stops. After maintaining pressure for 4s, the sliding end is withdrawn. The friction interface achieves metallurgical bonding through plastic deformation, recrystallization, diffusion and other processes, and the welding process ends.

[0034] Step 3: Use turning technology to remove the inner and outer flash of the inertia friction welding joint of the high-temperature alloy rotating workpiece by utilizing the rotational motion of the weldment and the linear motion of the tool, so that the processed surface roughness Ra is less than 1.6μm.

[0035] Step 4: Perform solid solution strengthening treatment on the welded joint: heat to 1080°C at a heating rate of 500°C / h, keep warm for 2h, and then cool naturally to room temperature.

[0036] Step 5: Heat the solution-strengthened joint to the first-stage aging temperature of 760°C at a heating rate of 500°C / h, keep it for 6 hours, then cool it to the second-stage aging temperature of 650°C at a rate of 55°C / h, keep it for 1 hour, and then naturally cool it to room temperature.

[0037] Step 6: Conduct microstructure analysis and mechanical property test on the welded joint. Figure 3 As shown in the figure, it can be found that after solution aging treatment, the overall grain size tends to increase, the grains in the weld core zone are relatively uniform along the radial direction, and dynamic recrystallization occurs in the heat-affected zone on both sides of the tube wall to form equiaxed grains, thereby improving the radial inhomogeneity of the grains in this area. Figure 4 (b) shows the distribution and morphology of the strengthening phases in different regions of the joint under heat treatment. The secondary and tertiary γ′ phases gradually precipitate during the cooling stage, and the distribution of the strengthening phases in different regions of the joint is relatively uniform. The strengthening phase morphology in the weld nugget zone and the thermomechanical affected zone is mainly spherical, while the strengthening phase morphology of the parent material is mainly cubic. Figure 5 As shown in the figure, after solution aging treatment, the tensile strength of the joint at room temperature is evenly distributed along the radial direction, with the maximum difference of only 4.4MPa. The tensile strength is highest at the center of the tube wall, with a maximum value of 1520.3MPa, and the tensile fracture position is mainly concentrated in the base material area. Figure 6 Middle (b).

[0038] Embodiment 2:

[0039] Step 1: Before welding, use sandpaper of different grits to grind the surface of the high-temperature alloy rotating workpiece with an inner diameter of 28mm and an outer diameter of 62mm step by step. Immerse the grinded workpiece in anhydrous ethanol solution for ultrasonic cleaning for 15 minutes, then use a hair dryer to dry the surface and dry it for later use.

[0040] Step 2: Clamp the workpiece to be welded on the rotating end and sliding end of the machine tool respectively, ensure that the axes of the two coincide, and calibrate and adjust the concentricity of the workpiece. Set the inertia friction welding process parameters, the initial speed is 645r / min, the welding pressure is 320MPa, and the moment of inertia is 388kg·m 2After the flywheel drives the rotating end workpiece to reach the initial speed, the spindle drive motor separates from the rotating end and begins to enter the free parking state. At the same time, the sliding end workpiece is driven by the hydraulic servo to move toward the rotating end. Under the action of axial pressure, the surfaces to be welded rub against each other to generate heat until they reach a high-temperature plastic state. The high-temperature plastic metal at the welding interface is squeezed out of the interface to form flash. Under the continuous action of friction torque, the speed of the rotating end workpiece gradually decreases until it stops. After maintaining pressure for 4s, the sliding end is withdrawn. The friction interface achieves metallurgical bonding through plastic deformation, recrystallization, diffusion and other processes, and the welding process ends.

[0041] Step 3: Use turning technology to remove the inner and outer flash of the inertia friction welding joint of the high-temperature alloy rotating component by utilizing the rotational motion of the weldment and the linear motion of the tool, so that the processed surface roughness Ra is less than 1.6μm.

[0042] Step 4: Perform solid solution strengthening treatment on the welded joint by heating it to 1020°C at a heating rate of 500°C / h and keeping it at that temperature for 2h, then naturally cooling it to room temperature.

[0043] Step 5: Heat the solution-strengthened joint to the first-stage aging temperature of 700°C at a heating rate of 500°C / h, keep it for 6 hours, and then cool it to the second-stage aging temperature of 600°C at a rate of 55°C / h. After keeping it for 1 hour, naturally cool it to room temperature.

[0044] Step 6: Perform microstructure analysis and mechanical property test on the welded joint, and the test rules obtained are substantially the same as those in Example 1. The difference is that at room temperature, the maximum difference in radial tensile strength of the joint is 8.1 MPa, and the maximum tensile strength is 1514.3 MPa.

[0045] Embodiment 3:

[0046] Step 1: Before welding, use sandpaper of different grits to grind the surface of the high-temperature alloy rotating component with an inner diameter of 28mm and an outer diameter of 62mm step by step. Immerse the grinded workpiece in anhydrous ethanol solution for ultrasonic cleaning for 15 minutes, then blow dry the surface with a hair dryer and dry it for use.

[0047] Step 2: Clamp the workpiece to be welded on the rotating end and sliding end of the machine tool respectively, ensure that the axes of the two coincide, and calibrate and adjust the concentricity of the workpiece. Set the inertia friction welding process parameters, the initial speed is 645r / min, the welding pressure is 320MPa, and the moment of inertia is 388kg·m 2After the flywheel drives the rotating end workpiece to reach the initial speed, the spindle drive motor separates from the rotating end and begins to enter the free parking state. At the same time, the sliding end workpiece is driven by the hydraulic servo to move toward the rotating end. Under the action of axial pressure, the surfaces to be welded rub against each other to generate heat until they reach a high-temperature plastic state. The high-temperature plastic metal at the welding interface is squeezed out of the interface to form flash. Under the continuous action of friction torque, the speed of the rotating end workpiece gradually decreases until it stops. After maintaining pressure for 4s, the sliding end is withdrawn. The friction interface achieves metallurgical bonding through plastic deformation, recrystallization, diffusion and other processes, and the welding process ends.

[0048] Step 3: Use turning technology to remove the inner and outer flash of the inertia friction welding joint of the high-temperature alloy rotating component by utilizing the rotational motion of the weldment and the linear motion of the tool, so that the processed surface roughness Ra is less than 1.6μm.

[0049] Step 4: Perform solid solution strengthening treatment on the welded joint by heating it to 1140°C at a heating rate of 500°C / h and keeping it at that temperature for 2h, then naturally cooling it to room temperature.

[0050] Step 5: Heat the solution-strengthened joint to the first-stage aging temperature of 800°C at a heating rate of 500°C / h, keep it for 6 hours, and then cool it to the second-stage aging temperature of 700°C at a rate of 55°C / h. After keeping it for 1 hour, naturally cool it to room temperature.

[0051] Step 6: Perform microstructure analysis and mechanical property test on the welded joint, and the test rules obtained are substantially the same as those in Example 1. The difference is that at room temperature, the maximum difference in radial tensile strength of the joint is 10.2 MPa, and the maximum tensile strength is 1510.7 MPa.

[0052] Comparative Example 1:

[0053] Step 1: Before welding, use sandpaper of different grits to grind the surface of the high-temperature alloy rotating workpiece with an inner diameter of 28mm and an outer diameter of 62mm step by step. Immerse the grinded workpiece in anhydrous ethanol solution for ultrasonic cleaning for 15 minutes, then use a hair dryer to dry the surface and dry it for later use.

[0054] Step 2: Clamp the workpiece to be welded on the rotating end and sliding end of the machine tool respectively, ensure that the axes of the two coincide, and calibrate and adjust the concentricity of the workpiece. Set the inertia friction welding process parameters: initial speed is 645r / min, welding pressure is 320MPa, and moment of inertia is 388kg·m 2After the flywheel drives the rotating end workpiece to reach the initial speed, the spindle drive motor separates from the rotating end and begins to enter the free parking state. At the same time, the sliding end workpiece is driven by the hydraulic servo to move toward the rotating end. Under the action of axial pressure, the surfaces to be welded rub against each other to generate heat until they reach a high-temperature plastic state. The high-temperature plastic metal at the welding interface is squeezed out of the interface to form flash. Under the continuous action of friction torque, the speed of the rotating end workpiece gradually decreases until it stops. After maintaining pressure for 4s, the sliding end is withdrawn. The friction interface achieves metallurgical bonding through plastic deformation, recrystallization, diffusion and other processes, and the welding process ends.

[0055] Step 3: Use turning technology to remove the inner and outer flash of the inertia friction welding joint of the high-temperature alloy rotating workpiece by utilizing the rotational motion of the weldment and the linear motion of the tool, so that the processed surface roughness Ra is less than 1.6μm.

[0056] Step 4: Conduct microstructure analysis and mechanical property test on the welded joint. Figure 2 As shown in the figure, due to dynamic recrystallization, fine equiaxed grains are generated in the weld nugget zone, and the width and average grain size of the weld nugget zone increase from the center of the tube wall to both sides. In addition, there is obvious grain refinement in the heat-affected zone on both sides of the tube wall. Figure 4 (a) shows the distribution and morphology of the strengthening phase in different areas of the welded joint. The strengthening phase in the weld core area is almost safely dissolved. As it moves away from the weld core area, the secondary γ′ phase gradually increases and tends to be stable. Due to the increase in local strain energy, the morphology of the secondary γ′ phase gradually changes from spherical to cubic. Figure 5 As shown in the figure, the tensile strength of the joint at room temperature has a large gradient along the radial direction, with the maximum difference being 41.2MPa. The tensile strength is highest at the center of the pipe wall, with a maximum value of 1491.98MPa. The tensile fracture position is mainly concentrated in the heat affected zone, as shown in the figure. Figure 6 Middle (a).

[0057] By comparing Example 1 with Comparative Example 1, it can be seen that the solution aging heat treatment method proposed in the present invention can significantly improve the joint strength and radial uniformity. Specifically, the heat-treated grains tend to increase as a whole and the radial grain distribution is more uniform. The cooling stage promotes the precipitation of secondary and tertiary γ′ phases, and the content of strengthening phases in different regions of the joint is significantly increased and the distribution is more uniform. In addition, after heat treatment, the tensile strength of the joint is significantly improved at room temperature and the radial tensile strength gradient is significantly reduced. The tensile fracture positions in the weld state are concentrated in the weld core area, while the tensile fracture positions in the heat-treated state are concentrated in the base material area. The synergistic strengthening effect of solution + two-stage aging proposed in the present invention can significantly improve the strength and radial uniformity of the high-temperature alloy inertia friction welding joint.

[0058] Finally, it should be noted that the above embodiments are intended to illustrate the technical solutions of the present invention and do not constitute any form of limitation on the present invention. Those skilled in the art should fully understand that it is completely feasible to modify the technical solutions described in the above embodiments or to perform equivalent replacements on any part or all of the technical features therein. These modifications or replacements, as long as they do not deviate from the scope of protection determined by the claims of the present invention, should be regarded as reasonable extensions of the present invention.

Claims

1. A method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint, characterized in that: The following steps are involved: Step 1: Grind the surface of the high-temperature alloy rotating workpiece to be welded step by step, immerse the polished workpiece in anhydrous ethanol solution for ultrasonic cleaning, and then dry it for standby use; Step 2: Clamp the workpiece to be welded at the rotating end and sliding end of the machine tool respectively, and calibrate and adjust the concentricity of the workpiece; weld the workpiece to be welded; Step 3: Remove the flash inside and outside the inertia friction welding joint of the high-temperature alloy rotating workpiece to meet the process design standards; Step 4: Heat the welded joint to the solution temperature at a constant heating rate, then keep it warm, and then naturally cool it to room temperature; Step 5: Heat the solution-strengthened joint to the first-stage aging temperature at a constant heating rate, cool it to the second-stage aging temperature at a constant cooling rate after insulation, and naturally cool it to room temperature after insulation.

2. A method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint according to claim 1, characterized in that: The solution temperature is 1020-1140° C., the solution holding time is 1-6 hours, and the heating rate is 300-600° C. / h.

3. A method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint according to claim 2, characterized in that: The solution temperature is 1080°C.

4. A method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint according to claim 1, 2 or 3, characterized in that: The first-stage aging temperature is 700-800°C, the first-stage aging holding time is 4-10h, and the heating rate is 300-600°C / h.

5. A method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint according to claim 4, characterized in that: The second-stage aging temperature is 600-700°C, the second-stage aging holding time is 1-6h, and the cooling rate is 10-200°C / h.

6. A method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint according to claim 5, characterized in that: The first stage aging temperature is 760°C, and the second stage aging temperature is 650°C.

7. A method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint according to claim 1, 2, 3, 5 or 6, characterized in that: The high temperature alloy is a nickel-based high temperature alloy; the nickel-based high temperature alloy includes FGH98, FGH101, GH4065 or GH4169.

8. A method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint according to claim 1, 2, 3, 5 or 6, characterized in that: In step 2, the inertia friction welding process parameters are: initial rotation speed of 300-1000 r / min, welding pressure of 20-500 MPa, moment of inertia of 30-500 kg·m 2 .

9. A method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint according to claim 8, characterized in that: In the step 3, the surface roughness Ra after processing is less than 1.6 μm.

10. A method for improving the strength and radial uniformity of a high-temperature alloy inertia friction welding joint according to claim 9, characterized in that: The high-temperature alloy rotating workpiece is a tubular structure with an inner diameter of 20 to 100 mm and an outer diameter of 30 to 180 mm.

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